You know what happens when Lucy goads the “Peanuts” hero into kicking a football, then pulls it away. The futbol equivalent is to end up on one’s backside by not winning even a single match in the weird, home-and-home, aggregate-goal format in the conference semifinal round of the MLS post-season. In two playoff appearances, they are 0-for-4, not even needing to count goals to get to the exit.

After being eliminated in 2009 by Houston and in 2010 by Los Angeles, the Sounders will seek a breakthrough after what has been their most successful season by getting past Real Salt Lake, a series that begins at 7 p.m. Saturday at Rio Tinto Stadium in Sandy, UT., followed by a rematch Wednesday at Seattle’s Clink.

After finishing with the second-best regular-season record (18-7-9), as well as the championship of the U.S. Open tournament and qualifying for the quarterfinals of the CONCACAF Champions League, the Sounders are eager to shed the happy-to-be-here approach.

We plan on going a lot further in the playoffs than we have before, goalkeeper Kasey Keller said. Its a different mentality. Im not saying by any means that were looking ahead of anything. Salt Lake is a good team, and we know we need to be at our best. I feel maybe this year were at a better place starting the playoffs.

The championship attitude began to gain momentum on the road against RLS on May 28, when the Sounders won 2-1, starting a nine-match unbeaten streak that fixed them into second place in the West, behind the Los Angeles Galaxy, for the balance of the season.

But RSL responded well on Sept. 10 in Seattle, winning 2-1 in part because of a bizarre own-goal by Keller, who mishandled a shot attempt into his own net — the worst mistake of an otherwise stellar final season for the retiring local hero from Olympia.

But RSL, beset by injuries and a suspension, stumbled thereafter, going 0-4-2 over the final six games to give Sounders fans — and even the opposing coach — reason to believe the Sounders are favored.

“Seattle is a fantastic team,” coach Jason Kreis told the Deseret News. “They’ve done so many things really, really well this year, there’s no doubt they deserve to be considered favorite in this series and they have the points to prove it.”

Despite the winless streak, RSL (15-11-8) still finished third in the West. But because of the convoluted, 10-team playoff system, this round features a 2-vs.-3 seeding matchup. In MLS, the first three seeds in each conference skip the play-in round, which is comprised of the four teams with the next-best records regardless of conference. But that single-elimination round is over, and top seeds have to play two games against one another instead of lesser seeds.

In its own way, it’s at least as unfair as college football’s BCS system, and most of the players and coaches have disdain for it, including Kreis. But nothing will change before Saturday.

Kreis believes his team relishes being the underdog, a position they have operated from most of the season.

“Along the way, Real Salt Lake has gotten a few points this season as well,” Kreis said. “For all of our trials and tribulations, and suspensions and referees’ decisions and international call-ups and injuries, here we are third place in the league, and you can believe me when I say this  we’ve earned every single point we got this year.”

The Sounders will have their own bit of trouble Saturday.Mauro Rosales, the Argentine midfielder who has added a spark since his arrival — he is the Sounders’ assist leader with 13 — was carted off the field with a damaged right medial collateral ligament Saturday in the regular-season finale against Chiva USA. He was considered by coach Sigi Schmid to be “questionable” for Saturday.

Schmid also has to make a decision between incumbent Mike Fucitoand newcomer Sammy Ochoafor the second starting forward spot next to Fredy Montero. Ochoa has come off the bench to score two goals and may present a matchup problem for RSL.

Whatever the lineup, Keller is persuaded that the attitude is different.

“After we made the playoffs last year, we kinda let down a little bit,” he said. “This year we’ve been up there all year. There’s a belief that every time we step on the field, we’re going to win.”

Starting Saturday, the highest scoring team in the MLS (56 goals) has two chances to back up Keller’s words with deeds.

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